1. Field of the Invention
The present invention relates to a method for forming a color image. In this method, an image obtained in an image forming apparatus using charged particles, such as an electrophotographic apparatus, an electrostatic recording apparatus or the like, can be retransferred onto a final transfer material.
2. Description of the Related Art
Methods for transferring an image onto a three-dimensional object using a technique called image transfer have been widely known. For example, a hydraulic transfer method has been widely known. In this method, a water-soluble paste, such as dextrin or the like, is coated on a base material, such as paper or the like, and a required image is formed according to screen printing or the like on the coated film using acrylic ink. The paper having the image is soaked in water to dissolve dextrin, and the acrylic-ink image floating on water is transferred onto a three-dimensional object made of earthenware or the like. A case of directly applying a transfer material used in this method to electrophotography is also known. This transfer material comprises rice paper having a dextrin film formed thereon. After forming a toner image on the surface of the dextrin film by an electrophotographic apparatus, the transfer material is passed through an organic solvent capable of softening a resin within the toner, to provide the toner image with an adhesive force to a retransfer medium where the image is to be retransferred. Then, the toner image on the transfer material is brought in close contact with the retransfer medium, and water is supplied from the back side of the transfer material to dissolve the dextrin film, and to transfer only the toner image.
In such a transfer material comprising opaque paper having a water-soluble coated film formed thereon, it is difficult to perform alignment during image retransfer. In addition, the surface of the transfer material softens before forming the image due to moisture in the surrounding atmosphere, and the softened dextrin adheres to a photosensitive drum and the like within the electrophotographic apparatus. Furthermore, since the transfer material is sensitive to moisture in air as described above, the amount of expansion and contraction depending on the amount of moisture is large, thereby producing unnecessary shelf curling of the transfer material, and greatly degrading the property of passing/conveying paper within the apparatus.
In order to solve the above-described two problems, in Japanese Patent Laid-Open Application (Kokai) No. 4-361086 (1992), there is a proposal of a transfer material in which polyvinyl alcohol obtained by saponifying vinyl acetate is used instead of dextrin. The proposed transfer material is obtained by coating a silicone resin on paper, and coating a mixture of Kasesol O-5 (the name of a product made by Nikka Kagaku Kabushiki Kaisha) and a silicone antifoaming agent on the coated resin. In image retransfer, after forming a toner image on the coated film by an electrophotographic apparatus, the Kasesol film is stripped off from the base material, and the toner image on the coated film is brought in close contact with a retransfer medium.
Then, by providing heat and pressure, the resin within the toner image is softened to provide an adhesive force to the retransfer medium. After cooling the combined member comprising the transfer material and the retransfer member, an 80% aqueous solution of ethyl alcohol is supplied from the back side of the Kasesol film to reduce the adhesive force between the Kasesol film and the toner image, and to complete image retransfer.
According to this method, since the thin film having the toner image is stripped off from the base material, a substantially transparent film is obtained, so that alignment becomes easier.
In the above-described conventional approach, however, when the retransfer member is made of a material which has poor compatibility with toner, for example, metal, earthenware such as a tile or the like, or glass, it is very difficult to supply heat and pressure during image retransfer, resulting in a poor retransfer property such that, for example, it is difficult to transfer toner onto the retransfer medium, and toner after image retransfer tends to be easily removed. As a result, a sufficient retransferred image cannot be obtained.